Born in Catalonia in 1870, Portet was raised in Barcelona, Spain. He attended the University of Barcelona, then went to Buenos Aires, Argentina to teach. In 1895, after five years away, Portet returned to Spain and soon got involved in an insurrection. He fled to Paris where in 1896 he met Francesc Ferrer i Guàrdia, founder of the Escuela Moderna or Modern School movement. He returned to Barcelona to get information and report on the radicals being tortured there. He then returned to Paris where he ran the publishing house Ferrer had established. After Ferrer was executed in 1909, Portet led a mass demonstration in Paris in front of the Spanish embassy. Though Ferrer left him his house in Paris, his publishing house and stock in Barcelona, and shares in two companies to enable Portet to carry on Ferrer's work, Portet was arrested and expelled from France. Seeking to carry on the work of the Escuela Moderna movement, Portet fled to Liverpool, England where he taught Spanish at the Commercial College and Portet helped to set up an anarcho-communist school in the Toxteth Co-operative Hall.
In 1915, Portet met American radical and fellow exile, Margaret Sanger, in a Liverpool cafe. Though married with children, he began an affair with Sanger, who agreed to become the English director of Ferrer's Paris publishing firm. After the two travelled together to London, Wales, Paris and Spain, Sanger decided to return to Canada, pick up her children and then move with them to Paris to be with Portet. However, she was unable to return immediately, and a few months later the younger child, Peggy, died. In mourning, she delayed her return still longer. In the interim, Portet, suffering from tuberculosis, died suddenly on May 10, 1917 in a nursing home in Paris.
- Sanger, Margaret (Dec 1916 – Jan 1917). "Portet and Ferrer, Parts 1-2". Modern School: 136–149 and 157–160. Retrieved 3 April 2012.
- Archer, William (1911). The Life, Trial, and Death of Francisco Ferrer. New York. ISBN 0-89875-509-3.
- Holton, Bob (1973). "Syndicalism and Labour on Merseyside," in Harold R. Hikins, Building the Union, Merseyside 1756-1967. Liverpool: Toulousse Press. p. 127.
- Sanger, Margaret (1938). Margaret Sanger; An Autobiography. New York: W.W. Norton. p. 504.
- Sanger, Margaret (February 1917). "Portet and Ferrer, Part 3". Modern School: 184–187. Retrieved 3 April 2012.
- Avrich, Paul. The Modern School Movement: Anarchism and Education in the United States (Princeton University Press, 1980)
- Constant, Leroy, Los Secretos del Anarquismo: Asesinato de Canalejas y el caso Ferrer. Mexico, 1913.
- Heath, Nick. Lorenzo Portet, 1870-1914 http://libcom.org/history/portet-lorenzo-1870-1917
- Katz, Esther, Cathy Moran Hajo and Peter Engelman, eds. The Margaret Sanger Papers Microfilm Edition: Smith College Collections (University Publications of America, 1996)
- Katz, Esther, Cathy Moran Hajo and Peter Engelman, eds. The Margaret Sanger Papers Microfilm Edition: Collected Documents Series (University Publications of America, 1997)
- Katz, Esther, Cathy Moran Hajo and Peter Engelman, eds. The Selected Papers of Margaret Sanger, vol 1: The Woman Rebel, 1900-1928. Urbana:University of Illinois Press, 2003. ISBN 0-252-02737-X